count_chars Return information about characters used in a string mixedcount_chars stringstring intmode Counts the number of occurrences of every byte-value (0..255) in string and returns it in various ways. The optional parameter mode default to 0. Depending on mode count_chars returns one of the following: 0 - an array with the byte-value as key and the frequency of every byte as value. 1 - same as 0 but only byte-values with a frequency greater than zero are listed. 2 - same as 0 but only byte-values with a frequency equal to zero are listed. 3 - a string containing all used byte-values is returned. 4 - a string containing all not used byte-values is returned. ]]> This will output : See also strpos and substr_count.